The present invention relates to radiation beam therapy systems and more particularly to a patient support for positioning and repositioning a patient in the exact same position for successive radiation treatments.
United States Patent Application Serial No. 07/163,611, filed Mar. 3, 1988, and assigned to the Loma Linda University Medical Center, describes and illustrates a radiation beam therapy system. The Loma Linda system includes several different treatment stations each including a gantry for supporting and rotating a radiation beam transport and delivery system on an axis of rotation around a stationary patient to deliver a treatment beam to a predetermined target isocenter within the patient from several different angles. The radiation beam described in the patent application is a highly concentrated proton beam which may be focused to release substantially all of its energy at pre-determined isocenters within a target range of 1 mm. Because of the high beam concentration and energy release control provided by the Loma Linda system, it is ideally suited for the treatment of cancer patients wherein proton beams are precisely focused at and irradiate diseased tissue without damaging surrounding healthy tissue.
With the Loma Linda system, a unique treatment plan is first developed for each cancer patient. In the development of a treatment plan, the patient may be positioned on a support table and the internal anatomy of the patient's body scanned as with a computed tomography device (CT Scanner). Images produced by the CT Scanner are analyzed to precisely locate the cancer sites defining the targets for the proton beams. Following the diagnostic CT study, examining physicians develope a radiation treatment plan calling for a number of different patient treatment sessions with proton beams of different magnitude, duration and direction. For each radiation treatment, it is important that the patient be supported in the exact same position as during the CT study utilized in the development of the treatment plan ("original position").
In the above referenced patent application, the patient support is diagrammatically illustrated as comprising a table. While a table may be moved vertically and laterally to position a patient, alone it is not capable of exactly repositioning a patient to the original position within a range of about 1 mm as required by the Loma Linda system. Accordingly, there is a need for a patient positioning and repositioning support for fixedly securing a patient in an original position during radiation treatment and for repositioning the patient in the same original position during subsequent radiation treatments. For radiation treatment systems, such as the Loma Linda system, which are designed to irradiate different portions of a patient's anatomy from several different angles, it is desired that the patient positioning and repositioning support fixedly secure the patient in a supine position. This requires that the whole body of the patient be fixedly supported.
Heretofore, patient positioning and repositioning supports have most commonly supported only predetermined portions of a patient's body. Whole body supports have been relatively complex, expensive and have not been capable of the precise patient repositioning required by proton therapy systems.
An example of a support system for predetermined patient body portions is the ALPHA CRADLE MOLD MAKER marketed by Smithers Medical Products Inc. of Akron, Ohio. In the Alpha Cradle system, a flat board having an open grid pattern of grooves is laid on a horizontal table. A plastic bag included in the system is opened and a foaming agent poured into the bag. The bag is then laid on top of the board and the foaming agent smoothed within the bag. Next, a patient is positioned on the table with a predetermined body portion, e.g. head and neck, resting on top of the bag. As the foaming agent expands, a technician shapes the bag about the body portion and blocks the bag against lateral expansion by placing small vertical wall members in the grooves along marginal edges of the bag. The patient lies motionless for about 15 minutes until the foam has cooled to room temperature and a solid mold of the body portion formed by the foam within the bag. Then the body portion may be removed from the mold which is now suitable for use in positioning and repositioning the body portion for successive radiation treatments. Patient positioning and repositioning supports similar to the Alpha Cradle system are employed at the Harvard Cyclotron Laboratory in association with Massachusetts General Hospital in Boston, Massachusetts.
A whole body support system has been employed by the Swiss Institute for Nuclear Research (SIN). The SIN system includes rigid fiberglass semi-cylindrical bottom and top portions forming a cylindrical tube for positioning a patient. The cylindrical tube is intended to be reused for different patients. To support the body of a patient within the cylindrical tube, the SIN system includes a number of rigid foam inserts each have a shape conforming somewhat to different portions of a patient's body. By selectively positioning a number of the inserts within the bottom semi-cylinder, a mold is formed which approximates the general shape of a back-side of a patient. A plastic liner is placed over the mold and a foaming agent introduced under the liner for foaming while the patient lies thereon. The result is a whole body mold which conforms closely to the shape of the back-side of the patient and which may be used in the positioning and repositioning of the patient within the cylindrical tube for radiation treatments. The SIN system utilizes a radiation beam that is rather diffuse. Therefore, it is not critical that the patient be repositioned to exactly the same position for each subsequent radiation treatment and means are not included in the SIN system for exactly repositioning the patient to the original supine position.
Accordingly, a need exists for a whole body patient positioning and repositioning support for fixedly securing a patient in an original supine position during radiation treatment and for repositioning the patient to the same original supine position for subsequent radiation treatments. Preferably, the support should be simple in design, easily assembled, and relatively inexpensive. Further, ideally, the support should incorporate means for readjusting slightly the position of the patient in the support to the original supine position prior to subsequent radiation treatments. The support of the present invention satisfies such needs.